Mobile and cellular telephones have come into common use today. Such equipment enables the provision of convenient telecommunications services to persons traveling in a vehicle or otherwise remote from traditional stationary telephone equipment.
To provide these services, cellular and mobile wireless communications systems generally employ a number of remote stations (often referred to as mobile stations or customer premises radio units) and one or more stationary units or base stations. The remote stations generally have the ability to establish communications links with the base stations, and the base stations are capable of establishing one or more communications links with a public service telephone network (PSTN), thus enabling the user of a remote station to communicate remotely with conventional telephones or other remote stations connected to the network.
The remote station typically comprises a cellular phone including a battery-operated transmitter/receiver, or a mobile phone, a similar device which is fixed to an object, usually an automobile. However, it is not uncommon, particularly in rural communities, for remote units to comprise stationary customer premises radio units (CPRUs). To initiate a telephone call on the public service telephone network (PSTN), a remote station will generally establish a communications link with a base station and the base station, often via a base station controller, cluster controller or control station, will establish a communications link with the public service telephone network. An exemplary wireless telecommunications system is described in U.S. Pat. No. 5,497,424, entitled "Spread Spectrum Wireless Telephone System," which is hereby incorporated by reference.
While providing convenient telephone services, present wireless telecommunications systems have limitations. Unlike traditional stationary telephones, in which the location of the telephone is inherent in the telephone number assigned to it, remote stations operating within a wireless environment do not have such information available. Moreover, because remote stations often have the ability to move and to establish communications with many base stations as they move through a network of communications cells, absent the use of global positioning systems (GPSs), there is presently no way to know the precise location of a remote station, unless the user of the remote station is somehow able to provide that information.
For example, if a mobile station user needs emergency assistance, the user may use the mobile station to call 911 or otherwise seek help. If the user knows his or her precise location, that information may be conveyed to emergency personnel allowing aid to be rendered fairly quickly. If, however, the user is lost or is somehow incapacitated, for example, if the user is rendered unconscious after initiating a call, information concerning the user's location may not be obtained, substantially increasing the likelihood that the user will not receive the needed emergency assistance.
In addition, if a remote station is lost or stolen, there is presently no practical way for the owner of the remote station or the wireless network service provider to locate the remote station.
Thus, there is a substantial need for a wireless telecommunications system that is capable of determining the precise location of a remote station.